1. Field of the Invention
The present invention relates to a vibration power generation device that generates power by converting vibration energy to electric energy, and particularly to a magnetostrictive vibration power generation device that uses a magnetostrictive effect by deformation of a magnetostrictive element.
2. Description of the Related Art
From the past, vibration power generation devices that convert vibration energy to electric energy and use it have been proposed, and research and development has been progressing to handle the increase in demand for energy saving in recent times. These vibration power generation devices are equipped with a power generating element for converting vibration energy to electric energy, but as the power generating element, in addition to piezoelectric elements, magnetostrictive elements are also used. A vibration power generation device using a magnetostrictive element, as shown in International Publication No. WO 2004/015790, for example, the structure is such that a magnetic path is formed that contains a rod shaped magnetostrictive element, a coil is wound on the magnetic path, and a permanent magnet is arranged to apply a bias magnetic field on the magnetic path.
However, with the permanent magnet, in addition to being directly fixed to the magnetostrictive element in order to apply magnetic flux to the magnetic path containing a magnetostrictive element as shown in WO 2004/015790, typically, this is also fixed to a yoke member fixed to the magnetostrictive element or the like to apply a vibrational load.
However, a typical permanent magnet formed with ferrite sintered body or the like is inferior to the load bearing capacity, so when the permanent magnet is arranged on the magnetic path for which the vibrational load is input, there is a risk of damage.